The present invention relates to an image forming apparatus such as a color laser printer, and in particular to an image forming apparatus including an intermediate transfer belt.
An image forming apparatus such as a laser printer is generally known, which comprises a plurality of development devices each containing different color toner, a plurality of photoconductor drums each of which is supplied with toner from a corresponding development device via a developing roller, a conveyor belt arranged opposite to the plurality of photoconductor drums, and a plurality of transfer devices configured to cause toner retained on the plurality of photoconductor drums to be attracted to the conveyor belt. In this image forming apparatus, the plurality of photoconductor drums are arranged in tandem, and a sheet of medium such as paper (hereinafter referred to as a sheet) is conveyed on the belt and passes between the plurality of photoconductor drums and the plurality of transfer devices, during which a transfer bias having the reverse polarity of the charged toner is applied to the transfer devices so that different color toner retained on the surfaces of the respective photoconductor drums is attracted by the transfer devices and continuously transferred onto the sheet to perform a color printing on the sheet.
Unlike the above image forming apparatus in which toner retained on the plurality of photoconductor drums is directly transferred onto a sheet, there is also known an image forming apparatus of an intermediate transfer type in which toner retained on each photoconductor drum is transferred onto an intermediate transfer belt to form a toner image and the toner image is then transferred from the intermediate transfer belt onto a sheet.
According to these image forming apparatuses, in order to ease maintenance of the photoconductor drums, each of the photoconductor drums for different colors is integrally held in a photoconductor drum unit, and this photoconductor drum unit is attached to or detached from a main body of the image forming apparatus. Further, in order to remove substance such as toner and paper dust adhering to the conveyor belt or the intermediate transfer belt (hereinafter these belts may be referred to as a belt) due to sheet jamming, etc., the image forming apparatus is also provided with a cleaning unit configured to contact with the belt to remove and collect the adhering substance.
For example, Japanese Laid-open Patent Publication No. 2006-98772, which corresponds to U.S. 2006/0067734 A1, discloses an image forming apparatus in which a photoconductor drum unit is arranged above a conveyor belt and a cleaning unit is arranged at a lower position of the conveyor belt where a sheet does not pass through.
However, an image forming apparatus including a cleaning unit requires maintenance of the cleaning unit in order to dispose of adhering substance that has been removed and collected from the belt.
However, in the above image forming apparatus, because the cleaning unit is arranged below the belt, it is necessary to remove the belt during the maintenance of the cleaning unit. Therefore, the maintenance work becomes complicated and time-consuming.
Further, according to an arrangement where the photoconductor drum unit is arranged above the belt and the cleaning unit is arranged below the belt, the height of the image forming apparatus is increased and thus the overall size of the image forming apparatus is enlarged.
In view of the foregoing drawbacks, the present invention seeks to provide an image forming apparatus, which can ease the maintenance work of a cleaning unit and which can reduce the overall size of the image forming apparatus.